Signal for telephone switching systems.



No.' 684,289. Patented oct. 8, mol.

, F. R. McBEnTY'.

slaan ron TELEPHonE swncmue svsrems.

(Applica-tion Bled In. 28, 1899.)

(No Modal.)

|nve nto r: '35m/rf, QR 88e@ his A117? Witnesses' 5 nois, have inventeda certain new and use- In a former patent, No. 567,404, dated Sep-UNITED 4STATES PATENT OFFICE.

FRANK R. MCBERTY, OF EVANSTON, ILLINOIS, ASSIGNOR TO THEWESTERN ELECTRICCOMPANY, OF CHICAGO, ILLINOIS.

. SIGNAL Fon TELEPHONE swli-CHING SYSTEMS. Y

'sPEcmIcA'rIoN forming pare of Letters Patent No. e4,2s9, dated octobere, 1901.`

Application led .Taimry 26. 1899. Serial No. 703,462. (No model.)

To a/ ZZ whom, at may cor'wen: e fone for. each line'liefore eachdistributing Be it known that I, FRANK R. MCBERTY, a operator. It is tothis feature of the call-discitizen ofthe United States, residingatEvans? tributing system that the present invention ton, in the countyof. Cook and State of Illi applies. 5S

ful Improvement in Signals for Telephone tember 8, 1896,*(Case 34,) Ihave described Switching Systems, (Case No. 58,) of which f and claimeda device by which the switching the followingis'a full, clem-,.eoncise,and ex operators act of connecting her telephone act description. with atrunk -line in position to receive oi-, 6o lo My invention concerns thetype of switchders from a calling subscriber automatically ing systemfor telephone-exchanges known as sets the signal associated with thetrunk-line the call-distributing system, and has for before thedistributing operator to indicate its object to prevent interferencebetween di'f-y that the switching operator is ready to referentcall-distributing operators. ceive connections. The even distributionof65 l5 The system referred to comprises an anwork among the differentswitching operators nunciator or distributing board wherein are is thusfacilitated'by the device for continuloeated call-indicating instrumentsfor all the ously informing the distributing operator of lines enteringthe central oce and switchthe busy or idle condition of the dilferentboards, preferably of the multiple type, in switching operators. -v zo'each of which are spring-.jacks or terminals The present inventionconsists in the comof all the lines and trunk or transfer linesbination, 'with this signaling mechanism for from the annunciator-boardto each ofthev signalizing to the distributing operator the multipleboards, with means for connecting idle condition of a switchingoperator,of mulone terminal of the trunk-line with any line tiple terminals forthe trunkf-line before dif- 75 z5 of the annunciator-board and the otherterferent operators, a signal associated with minal of the sametrunk-line with any line each of the terminals, and mechanism wherein asection of the multipleboard. A call by the act of connecting eithertrunk-line from a station is observed at the annunciawith anysubscribers line performed bya distor-board, and thereupon the line isextended -tributing operator indicates the use of the 8o 3o by theoperator at the annunciator-board trunk-line to the otherdistribntingoperators through `the agency of a trunk-line to any opand prevents themfrom using the line,where erator at the multiple board, who may hapbyinthe event of unintentional disregard of pen to be free to make newconnections, the the signals or simultaneous action on the part objectof that processbeing to 'attain even of distributing operators a signalshall be 85 35 distribution of the work of switching lines displayedbefore one of the operators, the obinto connection among the dierentoperators ject being to prevent two distributing operav at the multipleboard. There will of course tors from connecting a single trunk-linesibe as many distributing operators at the anmultaneously with the linesof two calling nunciator-board as may be necessary to transsubscribers.9o 4o fer the calls to the operators at the multiple The invention isrepresented diagrammatboards and as many of these latter operatorsically in the attached drawing in association as may be necessary tocomplete and superwith a switchboard provided with means for A vise theconnections. automatically operating signals in the switch- When thereare several distributing operaboard. Two lines are shown, each connected95 45'tors, it is essential to the eiicent operation with an instrumentcontrolling a signal in of the system that each of the distributing theannunciator-board, with a socket in the operators have access totrunk-lines to all annunciator-board, and withasocketin each theswitching operators. To this end it is deof the three sections of themultiple switchsirable that trunk or transferlines to each of board.` Atrunk-line is shown extending roo 5o the switching operators shallappear in the between the annunciator-board and one of multipleterminals at thc distributing-board, the sections of the multiplelboard, the trunlc.

lines appearing intbrice-multipled terminais in the annunciator-boardfor the use of three distributing operators. he drawing represents alsothe terminal plugs of another trunk-line multiplcd before the same threedistributing operators and extending to adiierent multiple section,together with the signal-lamp of this truuk-line at a multiple section,the ci-rcuits of this trunk-line having been omitted to avoidcomplication of the drawing.

Each substation is provided with the usual telephones and signalingapparatus, the appliances and circuits being arranged toclosetheline-circuit as to continuous currents only during the use of thestation-telephone. The line conductors from' cach station are connectedw'th the line-contacts of a terminal in the annunciator-board A and inother sockets a', a2, and a in the sections A', A2, and As in the 1nultiple switchboard. Line conductors are extended through the windingsof avrelay l1, which controls a local circuit includng a secondarylamp-signal c, associated with the corresponding line-socket in theannunciator-board. This local vcircuit is made up of conductors 3 and 4,the former of which is a ground branch including the resistance-coil andthe latter of which is a conductor leading to the free pole of agrounded source d of current and including the lamp c. The lever of therelay is connccted also by a wire 5 with the thimbles of vall terminalsockets (1,0', a2, and a.3 of the line.

The line-circuits, spring-jacks, and line-signals of two telephone-linesare shown.

A number ot tru nk or transfer lines G 7 extend between the aununciator-board and each section of the multiple switchboard. Eachtrunk-line terminates .in a plug e at the multiple switchboard and isbranched to three plugsf", and f2 at the annunciator-board. These plugsare designed for the use of three different distributing operators,giving each of them access to the switching operator havin'g charge ofthe corresponding trunk-line. There will of course be a sufficientnumber ofdistributing operators to distribute all calls received at theannunciator-board to switching operators at the 1n ultiple sections. Adistributing operator can thus distribute as many as seven thousandcalls pei-day. Hence in anexchange the number ofdistributing operatorsrequired at the annunciator-board will be determined by dividing thetotal number of calls received at the ann'unciatorboard in a day byseven thousand.- Inasmuch as au even distribution of the calls among theswitching operators necessitates her receiving calls from each off thedistributing operators, the trunk-lines to each of the switchingoperatorsshould appear before each of the distributing operators. Hencethe equipment of plugs for each trunk-line represented inthe drawing issu'ticient for an exchange having something over twenty thousand callsper day.

To transact such an amount of' vbusiness as `this would' require moreswitching operators than represented in the drawing, but this wouldmerely involve a larger number of trunk-lines. A switching operator cananswer three thonsan d calls and make the required connections per day.Hence sevensections of multiple switchboard will be required and sevengroups of trunklines extending froln the multiple switchboards to the annunciator-board, each trunkline appearingin three terminals at theniultiple switchboard.

The tru 11k-line is provided at the switchingoperators station with theusual calling-key (not shown). for connecting a generator ofcalling-current with the terminals of plug e and with a listening-key hfor connecting the operators telephone with the trunk-line.

I will now describe the local circuits involved in signaling betweenoperators al: the

different boards and between subscribers and operators.

Each plug is provided with a contact-piece 'L' in addition toitsline-contacts, designed to register with the thimblesor contact-rings kof the spring-jacks. The contact-piece i of plug e forms the terminal ofa wire 8, leading to the free pole of battery d. This conductor 8traverses an incandescent lamp Z, which is associated with the plug e inthe switchboard and constitutes a supervisory signal. The mode ofoperation between the line-signal c and the supervisory signal Z iswellknown to those familiar with existing telephone-switchboards,but may bebriefly described. The current from battery CZ through wires 3 4 of alocal circuit, which may become closed at a line-relay, is suicienttolight one of the signal-lamps used in the system; but wheneverconductor 8 becomes connected with wire 4 through the agency ofcontact-pieces i and 1c ofa pluginserted in a spring-jack lamps c and lare brought into parallel, both being in series with the resistance-coilin wire 3, under ,which condition neither lamp receives suft- `cientcurrent to light it.

If during the existence of these conditions the line-relay become inei tand separate the-conductor 3 from the wire 4, the full current frombattery d will be diverted through wires 8 and 3, whereby Ihesupervisorylamp l will become lighted.

A signal-lamp is associated with each of the plugs f, f', and f2, whichform the terminals ofi the trunk-line at the annunciatorboard. Theselamps are designated m, m', and lm2, respectively. These lamp-signalsare included in a local circuit associated with the correspondingtrunk-line whose continuity is normally controlled by switch-contacts on'the lopenators listening-key, these contacts being adapted to close thelocal cir- `cuit to livht the lam s m, m and 'm2 when e p a the operatorconnects her telephone with the trunk-line. The circuit is alsocontrolled by plug-seat switches of plugs f, f', andfz. Theswitch-levers of they listening-key h are pro- IIO vided with anauxiliary switch-contact h', which plays between two contact-pieces h2and h5, being thrust against the contact h2 when the key is putinposition to connect the operators telephone in a bridge of the trunkline6 7. Contact-piece h2 is connected by wire 9 with the free pole ofbattery d. The lever h is connected by wire 10 with the switch-lever ofa plu g-seat switch n of plug f. The normal resting contact of thisswitch is connected with the switch-lever of a similar switch n of plugfby wire 11. The resting contact of the last-mentioned switch isconnected with the lever of switch n2 of plug f2 by wire 12. The restingcontact of the switch fn,2 is connected to earth through wire 13, whichincludes serially the signal-lamps m2 Im m, associated with plugs f2 ff. Thus while the listening-key is in position to connect the operatorstelephone with the trunkcircuit and plugs f, j", and f2 are in theirresting-sockets a circuit will be complete from battery d through wires9, 10, 1l, 12, and 13 to light the lamps m, m', and m2. The sleeve 1l ofeach' of the plugs f, f', and]c2 is connected with the wire extendingfrom wire 10 to the plug-seat switch of the same plug- Aso namely, thesleeve of plug f is connected with wire 10, the sleeve of plug f withwire' 11, and the sleeve of plug f2 with wire 12.

The alternate contact-piece h3 of the lever h on the listening-key formsthe terminal of a conductor 14, which is connected with wire 9, and thusis completed to the free pole of battery d, which includes a supervisorysignal-lamp p, also associated with plug e in the switchboard, and whichis controlled by a plug-seat switch ofplug e.

Clearing-'out lamps q, q, and q2 are associated with the plugsf, f', andfrespectively, in the switchboard. These lamps are located in multipleearth branches of the conduct-or 16, which terminates in a contact-pieceof a plug-seat switch of the plug e. Each of the earth branches iscontrolled by switch-contacts of the plug-seat switch of the plug n, n",or n2, with which the lamp q, q', or q2 in question is associated, theseswitch-contacts being arranged to open the ground branch including thevlamp when the plug is not in use. The plug-seat switch rr' of plug e isar- -ranged to connect the wire 16 with the wire 15,

leading by way of wire 9 to battery d, when yplug e rests in its socket.Hence the general circuit, including the clearing-out lamps q, q', andq2 of a trunk-line, is established when the terminal plug e of thetrunk-line is replaced in its socket, and the branch, including theclearing-out lamp of the particular terminal plug at thedistributing-board which may be in use, is closed during the use of thatplug.

I will first briefly trace the general mode of operation of the system.Any switching operator who may be free to receive calls and makeconnections indicates this vfact to the distributing operators byconnecting her telephone with a trunk-line by means of herlistening-key, whereby the lamp-signals associated with the trunk-lineat the distributingboard become lighted. A subscriber at one stationwishing to obtain connection with a'nother station takes his telephonefrom its hook, which act causes the illumination of a lamp in theannunciator-board associated with his line. The distributing operatorobserving this signal makes connection With a spring-jack of thecalling-line by means of some trunk-plug of which the associated lamphad been lighted, whereby the calling-line is, in effect, extended to aswitching operator who is free to attend to the subscribers wants andwho already has her listening-telephone connected with the trunk-line,such connection of the telephone with the trunk-line being the cause ofthe lighted condition of the signals fm/m m2. The waiting operatorimmediately demands the number of the line with which connection isrequired and after receiving it makes the usual test and establishesconnection with the required line at the multiple switchboard.Thereafter this operator supervises the connection by means ofsignal-lamps associated with the trunkline through which the requiredconnection has been established.

Any of the several distributing operators may observe the subscriberscall and attempt to trunk the call to some switching operator. It twodistributing operators should attempt to make connection with lines oftwo calling subscribers by means of plugs of the same trunk-line, onlyone of the connections would be effective. The lighted signal-lamp ofthat subscriber would become extinguished, while the line-lamp of theother subscriber would remain lighted, its illumination being anindication to the distributing operator that another operator hadobtained the useof the trunk-line. Thus the mechanism prevents confusionwhich might arise through the accessibility of every trunk-line to eachof several distributingoperators. When theswitching operator removes theconnection with the called line, the distributing operator who made theconnection between the same trunkline and the calling-line is apprisedot'- this fact by meansof a signal-lamp and withdraws the other terminalof the trunk-line from the spring-jack of the calling-line.

I will now trace the operation in greater detail,fo1lowing the circuitsthrough the various changes involved in making and breaking IOO IIO

When the switching operator at the switchboard;A', for example, is readyto make connections, she brings her telephoneintoconnection.withthetrunk-line G 7 by meansof key h. This actconnectsV contact-piecesV h and hthus completing'acircuit 9 l0 1l l2 13through the lamps m, mr', and. m?. The lamps mentioned therefore becomelighted, indicating to the different switching operators that thetrunk-line to which they refer is free for use and that. the operatorhavingj charge ot' it is ready to receive calls. A sub scriber callingcloses his line-circuitfas to the central source of calling-current whenhe raises his telephone from its switch, exciting the relay b andclosing the circuit` 3 4. Linelamp c is thuslighted, which constitutes acallfto the distributing operators. A. distributing operatorfor example,the one having access to plugf-seeingt-he lamp m lighted: beside theplug f raises this plug from its socket and inserts `itintov thespring-jack ctof the calling-line. A circuit through 'wires 9 and 10 isthus brought into shunt about wire 4, including the line-lamp, andin'series` with the wire 3, whereby the line-lamp isshort-circuited andextinguished. The act. of raising the plugffrom its socket permitted theplug-seat switch n. to break connection` between Wires 10 and 11,whereby theV circuit through lamps m, m', and m2 is broken and permitsthese lamps to become dark. The same switchcloses the circuitthroughclearing-out lamp q, associated Withplugf, which becomes lighted,but its signal is ignored until the operator at switchboard A shall havehad suiicient time tomake the required connection. The extinction ofline-lamp c indicates to the distributing operatory who, inserted plugfthat the connection has been. properly made.l If: the operator beforewhom plug f is stationed, having seen the lighted lamp m' and wishing touse atrunk-line, had employed plugf'to make connection with the line ofa calling subscriber, the shunt-circuit 9 10 would be found disconnectedfrom the sleeve 'i of plug f, so that the lamp c of thecalling-subscribers line would remain light-V ed. This would indicate tothe operator who had made the connection that another operator hadobtained the same trunk-line at nearly the same moment, and the operatorwould withdraw plug f of that trunk-line from the spring-jack of thecalling-line and insert a plug of another trunk-line which was ready foruse in place of it. If the plug f' should be used in making aconnection, the use of the plugf a moment later would practically leavethe connection with the plug f, ordering outplug f-that is, theplugfwould` bring about the extinction ofthe lamp of the line with whichit was connected, while the lamp of the line with which plug f' wasconnected would become lighted and would call for the disconnection ofthat plug. The oper.- ator at switchboard A, to whom the call has thusbeen transferred, receives the callingsubscriber-s order for therequired connec# tion, tests the. line calledifor` in thek multiplesw,itchboard,and makes connection therewith (assuming that she has foundit free for use) in the usual Way, after which she disconnects hertelephone. The raising of plug e from, its seat breaks connectionbetween wires 15 and 16, depriving the-clearing-out lamp q of current,and also permits the contacts fr r2 to close the break in wire 14.disconnection ofY the operators telephone by. means of thelistening-keyclosesconnection between wires 10 and 14, thus completinga-V circuit,through the supervisory signal-lamp Itgwill be observed that thislamplpis now in parallel with the line-lamp c. The current, throughconductorv 3 isidividedibetween these twov lamps, so that. both-remaindark. The insertion of, plug e into aspringjack of the line called forbrings the lampi into parallel with the line-lampY otl the,l line Thesubsequent called for; but inasmuch-as the circuit through,

that lamp is broken at the line-relay, the subs.-

scriber called having not yet: responded, the lampvl is lighted bycur-rent fromrbatteryd throughwires 8 and 3. The response ofthe calledparty is indicatedpby the extinctionbfi lamp Z. Supervisory lampsp and Zthus serve as automatic indicators before theswitching operator ofthepositions-of the telephones at` the calling and called stations.` When`the calling subscriber 'replaces histelephone on its switch, his relay bis deprived of currentv and breaks the conductor 4, whereby the cur-Yrent of battery d is diverted throughfconducf. torsv9, 14, and 10,lighting the lamp p., Simi@ larly the replacement of the telephone ontsswitch at the calledV stat-ion will divert, theV 'current whichpreviouslyllowed through the line-lamp of that station into thesupervir. sory lampl,\vhereby thislamp will be lighted. Thesimultaneousillumination oflampsl and p may be accepted by the switching-operator asa signal for disconnection, after which she will remove the plug e'fromthe spring-jack` and replace it in its resting-socket. breaks thecircuit through lamp Zfat the sepa.- rated contacts i and. k of4 thespring-jack and plug, respectively, andv severs theV circuit throughsupervisory lamp p atthecontacts fr" r3 of the plug-seat switch fr., Thesame actv IOO IIO

This ,act

closes together the contact-pieces r' fr* ofi this switch, completing acircuit through Wires Y 15 and 16 to the plug-seat switch n, Where currvrent finds circuit through clearing-outlamp q and the registeringcontacts of plug-seat switch n to earth. Clearing-out lamp q is thuslighted. removal ofY plugf from the spring-jack of; the calling-line. 1fplug f orf hadv been em.- ployed in making connection with the calls`ing-line the corresponding clearing-out sig.

nal q or q2 would become lighted.

It will be observed that of1 thek series off plugsf, f,and f2 the plugfwouldalways, in effect, cut 0R the other plugs in the series, so thatthe distributing operator using plug f Its illumination calls'for the`would always deprive the other distributing i plug fat differentpositions at the annunci ator-board. These plugs in each position in thecircuit should be located before each of the distributing operators, sothat all distributing operators would find trunk-lines busy anapproximately equal number of times-that is, assuming, for' example,that three trunk lines terminated in multiple plugs before the threedistributing operators I would arrange plugfof one line, plugf' ofanother line, and plug jl2 of a third line before one of the operators;plug f' of the rst line, plugf2 of the second line, and plug f of thethird line before another operator, and plugf2 of the first line, plugfof the second line, and plug f of the third line before the thirddistributing operator, carrying out a similaiarrangement for a larger nmnber of plugs.

The invention is defined in the following claims:

1. In a call-distributing system comprising telephon e-lines,each havinga terminal socket and a signaling instrument in an annunciator-board,and a terminal socket in each of several sections in a multiple board, atrunkline extending from the annunciator-board to each section of theswitching-board, of multiple terminal plugs for each of the saidtrunk-lines at the annunciator-board,where by several distributingoperators have access to the same trunk -lines to equitably distributethe calls to the switching operators, as described.

2. The combination with a call-distributing system comprisingtelephone-lines, each having a terminal socket and a line-signal in anannunciator-board, and a terminal socket in each of several sections ofa multiple switchboard, and a trunk-line extending from theannnnciator-board to a section'of the multiple switchboard, of multipleterminals for the said trunk-lines at the annunciator-board, a signalassociated with each terminal, and a local circuit including the saidsignals, said local circuit being controlled by a switch associated withthe trunk-line at the section of multiple switchboard; whereby alldistributing operators are apprised of the readiness of a switchingoperator to receive calls, as described.

3. In combination with a call-distributing system comprisingtelephone-lines, each having a line-signal and a terminal socket in anannunciator-board, and a terminal socket in each section of a multipleswitchboard, and a trunk-line extending from each section of themultiple switchboard to the annunciator-board, of multiple terminals forthe said trunk-line at the annunciator-board, a signal associated witheach of said terminals, a local circuit including said signals, and aswitch at the multiple section controlling the said circuit and a switchconnected with each of said multiple terminals to be actuated in the usethereof also controlling all of said signals; whereby a switchingoperator may apprise all the distributing operators of her readiness toreceive calls, and the act of any distributingA operator in making useof the trunk-line may be signaled to the other distributing operators,as described.

4. The combination with tween switchboards, of multiple terminal plugstherefor at one switchboard, a signal associated with each of saidmultiple terminals, a circuit for operating the signal, a switchcontrolling the circuit at the distant terminal of the trunk-line, and aswitch associated with each of said multiple terminals controlling allsaid signals, as described.

'5. The combination with a trunk-line between switchboards, of multipleterminals at one extremity of the trunk-line, a signal associated witheach of said multiple terminals, a circuit for operating the saidsignals simultaneously, a switch at the distant terminal of thetrunk-line controlling the said circuit, and a switch connected witheach of said multiple terminals to be actuated in the use thereofadapted to render all of said signals inoperative when one of themultiple terminals is used, as described.

6. The combination with a trunk-line having a terminal at one stationand multiple connection appliances at the other station accessible todiierent operators, of signals c c with which the several connectionappliances are adapted to be temporarily associated, a circuit-changingdevice operated by each connection appliance when in use, and circuitsassociated with the several connection appliances adapted to be broughtthereby into temporary association with the several signals c c, saidcircuits being controlled by the aforesaid circuit-changing device,whereby the use ot one of said connection appliances is caused to effectthe operation of the several signals c c and so to indicate the busycondition of the trunk-line, as described.-

7. The combination with a telephone-line and the connection-socketthereof, of a signal near the socket, a link conductor having multipleterminals, each adapted for connection with the socket of a line,switches associated with each of said terminals to be made operative inthe use of the terminal, and circuit connections of the said signalcontrolled by the said switches adapted to vcause the display of thesignal near one of said terminals in a socket when either of saidterminals is brought into use; whereby one operator in making connectionwith a telephone-line is warned that another operator has madeconnection with a difereut line by means of the same link conductor, asdescribed.

8. The combination with a trunk-line having multiple terminal plugs atone station, of a plug-seat switch for each plug, a signaling atrunk-line be- IOO instrument adapted for association with any plug, andcircuit connections of said signal changed in the simultaneous use oftwo plugs adapted to operate the warning-signal at one of the plugs,whereby one of two operators attempting to make use ot` differentterminal plugs of the trunk-line willV be warned of the use of the line,as described.

9. The combination with subscribers lines and the terminal sockets andline-signals of each ot' said lines in a switchboard, of a linkconductor having multiple terminals adapted for connection with suchsockets, and circuit connections comprising a conductor including` oneof said line-signals, and switch-contacts operated in the simultaneoususe of two of said terminals completing the said circuit connections tocause the display of saidV signal; whereby one of two operatorssimultaneously using` the trunk-line is warned of such use by theline-signal, asdescribed.

10. The combination with aYtrunk-line extending between two stationshaving a single terminal plug at one station and multiple terminal plugsat the other station, of a signal associated with each of said multipleterminalsa local circuit including saidk signals, and` a switch at saidsingle terminal controlling the local circuit, a switch for each of saidmultiple terminals actuated in the use of the terminal, a signalassociated with one of said multiple terminals, and circuit connectionsof said signal controlled by the switch associated with another of saidterminals adapt-y ed to cause the excitement of said signal; whereby anoperator atthe said single terminal may-call to all the operators havingaclcessfto said multiple terminals, but the simultaneous use of saidmultiple terminals by two operators will bel indicated to one of saidoperators.

1.1. The combination with a link conductor for, uniting telephone-lineshaving multiple connectiony terminals at one end thereof, of aclearing-out or equivalent signal associated with each of the saidVmultiple terminals, al

device associated with each of the multiple terminals adapted to makethe signal associ'ated with the same terminal operative whentheter-minal is'in use, the condition of the remainingl signalsremaining unchanged, and meansfor controlling the circuits ot'said-signalgas described.

12. The combination with a link conductor fou uniting telephone-lineshaving lnultiple terminals at one end, of a clearing-out signalassociated with each. ot'l the terminals, a circuit common to saidterminals, and means associated with the other end of the trunk-line forcontrolling the operation of said clearingout signals, and adeviceassociated with each of saidmultiple terminals operated in the useofsaid terminal adapted to make the clearing-out signal associated withthe terminal operative during the use of the terminal, the conditionot'Ythe other clearing-out signals remaining unchanged, substantially as denconnecting-switch for the line', and a circuit of said line-signalformed temporarily through the connecting-switch, and a conductorassociated with the trunk-line to the distant terminal thereof, andmeans at the distantterminal for controlling the circuit thus formed;whereby the subscribers line-signal may be controlled through thetrunk-line, as described.

14. The combination with a telephone-line, a relay connected therewithto respond to currentin the line during its use, and asecondary signalcontrolled; by the-relay, anda spring-jack for the line, of a, linkconductor having multiple terminal plugs, a, circuit having multiplebranches to each plug adapted to be brought into shunt of thesignal-lamp .of a line through registering contacts of the plug andspring-jack, and a plug-seat switch of each ot' said multiple terminalplugs, havingV switch-contacts controlling the circuit of said branchesto all plugs but` its own, as described.A

15. In combination with a trunk-line, multiple terminal plugs thereof,and switches, one for each of said multiple plugs, aI signal and acircuit thereof traversingsaid switches in series, and an independentYswitch at the distant terminal station ofi said trunk-line controllingthe said signaling-circuit, substantially as described.

, 16. In combination with a trunk-line and vrmultiple terminal plugsthereof, al clearingout signal for each of the plugs and adswritch yforyeach plug controlled thereby, each, of

said clearing-outv signals beingV together withV .said switch of thesame plug in a multiple branch of the signaling-circuit, and independentmeans at the distant station of thez trunk-line, common to the differentsi,f. 'na.ls,

for controlling the signaling-circuit; whereby the clearing-out signalof any plug which is'in use is made operative tcp receive the isignalfor disconnection, substantially as d escribed.

17. The trunk-line circuit 6 7, provided at;

one end withmultiple plugs ff f2, switches. 'n n n2 for said plugs,respectively, a1 signalY and a signaling-circuit'thereof travel-singen:rial contacts of said switches, and independent means at the distantterminal off the trunk-line, for controlling said circui t,sul'pYstantially as described.

18., The combination withka trunk-line andi multiple terminal plugsthereof, of plug-seat switches n n n2, one for each plug, :ay-signal;-ing-circuit connected through said switches, clearing-ont signalsassociated with the dif.-` ferent plugs, and an individual. circuit of:

, each of said clearing-outsignals controlletlojyY IOO IIO

the plug-seat switch of the corresponding plug, a switch at the distantterminal of the trunk-line for controlling said signaling-circuit, and aclearing-out switch r controlling the general circuit of saidclearing-out signals, substantially as described.

19. The combination with a telephoneline, a relay therein responsive tocurrent in the line, a line-signal and a local circuit of the signalcontrolled by the relay, a plug and spring-jack for making connectionwith the line, and a conductor terminating in the plug, adapted to forma shunt about said line-signal when the plug is in the jack, and aswitch adapted to break the circuit of said conductor and prevent theshunting of the line-signal thereof, substantially as described.

20. The combination with a telephone-line, a relay in the lineresponsive to current therein, a trunk-line for making connection withthe telephone-line, and a supervisory signal at the distant terminal ofsaid trunkline, a circuit of said supervisory signal completed throughregistering contacts of the terminal plug of the trunk-line and thespring-jack of the subscribers line, said cir cuit being controlled bysaid relay in the subscribers line, and an operators listening-key alsocontrolling said circuit, as described.

21. The combination substantially as herein set forth, of atelephone-line and a relay therein, a trunk-line and means for makingconnection from each terminal thereof to a subscribers line, asupervisory signal associated with the distant terminal of thetrunk-line, and a circuit of said signal closed at one point in makingconnection from said trunk-line to said subscribers line,said circuitbeing controlled by the relay in the subscribers line, and a switchactuated in mak- [SEAL] Countersigned F. I. ALLEN,

ing connection with said distant terminal of the trunk-line, controllingsaid circuit ot the signal.

22. The combination with a telephone-line, a terminal spring-jackthereof and a line-signal associated with the spring-jack, a trunklinefor uniting telephone-lines, and a circuit of said line-signal closedthrough said springjack and a plug ot' the trunk-line when insel-tedtherein, a conductor of the trunk-line, and a switch at the distantterminal of said trunk-line, actuated in making connection with saiddistant terminal, controlling the circuit formed through said conductor,including said line-signal; whereby the subscriber-s line-signalindicates the formation of connection with the distant terminal of thetrunk-line, as described.

23. In a telephone-exchange system, the combination with trunk-lines,each provided with multiple terminal connections, any of said multipleplugs of a trunk-line being adapted to be connected with the spring-jackof a subscribers line, and cach being provided at its distant terminalWith a supervising-signal and having a circuit divided into multiplebranches terminating in the difterent multiple terminal connectionsthereof, a relay in each subscribers line, and a circuit controlledthereby adapted to be brought into connection with the circuit of saidsupervising signals of the trunk-line through the spring-jack of theline and one of said terminal plugs of the trunk-line, as described.

In Witness whereof I hereunto subscribe my 7 5 name this 30th day ofDecember, A. D. 1898.

FRANK. R. MCBERTY. Vitnesses:

ELLA EDLER, D. E. WILLETT.

F. L. CAMPBELL,

Assistant Secretary of the Interior.

Commissioner of Patents It is hereby certified that in Letters PatentNo. 684,289, granted October 8, 1901, upon the application of Frank B..McBerty, of Evanston, Illinois, for an improvement in Signals forTelephone Switching Systems, an error appears in the printed specicationrequiring correction, as follows: In line 66, page 4, the referenceletter A should read A and that the said Letters Patent should be readwith this correction therein that the same may conform to the record ofthe case in the Patent Qce.

Signed, countersigned, and sealed this 22d day of October, A. D., 1901.

It` is hereby certified that in Letters Patent No. 684,289, grantedOctober 8, 1901, upon the application of Frank R. McBerty, of Evanston,Illinois, for an improvement in Signals for Telephone Switching Systems,an error appears in the printed specification requiring correction, asfollows: In line 66, page 4, the reference letter A should read A' andthat the said Letters Patent Should be read with this correction thereinthat the same may conform to the record of the case in the Patent Qiice.

Signed, countersigned, and sealed this 22d day of October, A. D., 1901.

[SEAL] F. L. CAMPBELL,

Assistant Secretary of the Interior. Conntersigned:

F. I. ALLEN,

Commissioner of Patents.

